This paper aims to investigate consumer preferences for voice calling using two methods via mobile phone-Over-the-top (OTT) voice calling services using the Internet and mobile telephony using cellular networks in different situations-for both formal and casual occasions. In brief, it explores how users prioritize these attributes; service quality, price, and Internet connection requirements. A discrete choice experiment was conducted in Thailand in 2019 with 444 observations. The results reveal that respondents valued service quality most in both occasions, followed by price, and lastly Internet connection requirements. However, in regards to situations of formal usage, consumers valued service quality to a significantly higher degree than prices when compared with casual use situations. Hence, users rely on better quality services over low cost services. It can be implied that users are more likely to employ mobile telephony, the service quality of which is considered to be better, than they are to use OTT in casual situations compared to formal occasions. Implications of these results are also discussed in this paper.